'If you've ever wondered what a word processor does with your words, think about what a food processor does with your food'

And vi is a fine tool for someone who's comfortable writing at the HTML source code level. But it's unreasonable to expect all authors to be HTML experts, and nor should they have to be. It's a great shame if we're still at the stage with e-books where that should be the expectation. And I don't personally think we are.

I think you mean vim, which has syntax highlighting (or so I hear), not plain old vi.

My advice is not to worry too much about the program (they're all fine as long as they can export as HTML), and focus on the content instead. But if you wanna do it right, Adobe is considered the leader in desktop publishing. Get their Creative Suite and grab some tutorials from lynda.com. Of course, you can also talk to a publisher and they'll take care of it for you. But for a short story to put on your girlfriend's e-reader, any program is probably overkill.

Some people are over concerned with how beautiful the HTML is as opposed to how it appears on the reader. Calibre makes good looking epubs out of practically anything. But its HTML is not beautiful. Does the non-technical reader care? Not at all.

Since you have a Sony, you will want to check it on your PRS-350 to make sure things that look good on the computer screen look good in the ebook. You might download the older version of the reader for PC software from the Sony Reader site. It works better in my unhumble opinion for checking than the new software does.

One caution if you go back and forth between them- Sigil does not grab ownership of a file once open, so you can open it in the Sony Reader for PC at the same time. The Reader software does grab ownership and will cause an error in Sigil if you try to save while it is displayed in the reader. Just clicking on the list, rather than display of a particular epub will avoid this conflict.